<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

</body>
<script>
    var time = prompt('请输入几点钟')
    if (time == 12) {
        alert('中午好');
    } else if (time == 18) {
        alert('傍晚好');
    } else if (time == 23) {
        alert('深夜好');
    }
</script>

</html>